Some communication systems make use of multiple antenna elements at the transmitter and/or the receiver. For example, MIMO systems involve communication between a transmitter with multiple antenna elements and a receiver with multiple antenna elements. MIMO systems offer spatial multiplexing, diversity, and beamforming gains compared to systems with a single antenna element at the transmitter and the receiver.
In massive MIMO communication systems, base stations make use of arrays of antenna elements where the number of antenna elements is larger than a number of parallel streams being transmitted. For example, a base station in a multi-user (MU) massive MIMO system may have hundreds or even thousands of antenna elements simultaneously serving tens of users on a same time-frequency wireless resource.
Signal processing techniques, such as beamforming and precoding, can be used to shape the signals transmitted by a number of antenna elements. Typically, by shaping the signals transmitted by the antenna elements, a base station aims to have wave-fronts collectively emitted by the antenna elements to add up constructively at the locations of intended receiver terminals, and destructively (or randomly) in other locations.
Signal processing for signals to be transmitted by a number of antenna elements is typically performed by a baseband processor. The baseband processor outputs sequences of digitally modulated symbols. These sequences are provided as input, respectively, to radio-frequency (RF) transmit chains, each transmit chain comprising a power amplifier coupled to one of the antenna elements. As the number of antenna elements grows, the signal processing performed by such a baseband processor increases in complexity.